The research and test of the cavitation performance of first stage impeller of centrifugal charging pump in nuclear power stations

The safety production is the most important index for nuclear power development, and the CVCS (chemical and volume control system) occupies an important place in safety control system. The CCP (centrifugal charging pump) is an important component of CVCS system and its particularity decides the high requirements on the cavitation performance, so the research on CCP cavitation has great significance. Using the 3D Pro/E software, the paper makes models of the flow passage components of first stage prototype of CCP in nuclear power stations, and completes the cavitation steady-state computation in the case that the high flow rate of first stage prototype reaches Q=160m3/h using the numerical computation software ANSYS CFX. The cavitation is divided into the following five stages according to its development process: inception operating condition, development operating condition, critical operating condition, serious operating condition and fracture operating condition. The research analyze the flow field, static pressure fields and bubble distribution conditions in the impeller in different cavitation states, and selects the middle flow line, the front shroud flow line and the back shroud flow line from the same blade for the comparative analysis; to verify the reliability of computation, the researcher made a first stage cavitation prototype to verify its hydraulic performance and cavitation performance. After the comparative analysis on the flow field, pressure and bubble distribution conditions of CCP first stage impeller in different cavitation states, the research draws the following conclusions: (1) as the inlet pressure decreases, the cavitation degree increases, the bubble distribution area extends from impeller inlet to impeller outlet and shows different laws in different cavitation states; (2) the generation of cavitation is affected by the pressure changes in impeller passages, and when the inlet pressure decreases, the static pressure in impeller passage decreases, thus producing a local low-pressure area; (3) the comparison of computation and test results shows small errors, thus proving the accuracy of analog computation; besides, the research verifies the cavitation performance in different flow rates by test, and test results show that NPSH3 is smaller than the 7.8m stipulated in Technical Specifications in any flow rate condition, indicating that the design is reasonable. The research points out a direction for the further improvement of optimization design of CCP cavitation performance.